From: | "Boersenspielteam" <boersenspiel(at)vocalweb(dot)de> |
---|---|
To: | "Vadim B(dot) Mikheev" <vadim(at)sable(dot)krasnoyarsk(dot)su> |
Cc: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>, hackers(at)postgreSQL(dot)org, t-ishii(at)sra(dot)co(dot)jp |
Subject: | Re: [HACKERS] subselect and optimizer |
Date: | 1998-04-14 14:22:19 |
Message-ID: | 199804141222.OAA17040@binky.de.uu.net |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
Hi,
then I think this one is solved.
I'll try to reproduce it on my machine, if I get the same results, I
will be a quiet and happy Postgres user again ;-)
I don't have the message, that originated this thread, but is the
slow subselect from Tatsuo fixed?
Tatsua, can you test queries with the abckend options suggested by
Vadim?
> In current I see that
>
> Hash Join (cost=5905.62 size=3343409 width=8)
> -> Seq Scan on trans (cost=3154.70 size=71112 width=4)
> -> Hash (cost=0.00 size=0 width=0)
> -> Seq Scan on kurse (cost=238.61 size=4958 width=4)
>
> IS FASTEST plan ! Result is returned in ~ 56 sec.
>
> Nested Loop (cost=148934.30 size=3343409 width=8)
> -> Seq Scan on trans (cost=3154.70 size=71112 width=4)
> -> Index Scan on kurse (cost=2.05 size=4958 width=4)
>
> returns result in ~ 80 sec.
>
> Merge Join (cost=7411.81 size=3343409 width=8)
> -> Index Scan on kurse (cost=337.90 size=4958 width=4)
> -> Index Scan on trans (cost=4563.60 size=71112 width=4)
>
> is SLOWEST plan (~200 sec).
>
> Please don't think that using indices is the best way in all cases...
>
> BTW, you can use -fX _backend_ option to forbid some join methods -
> I used '-o -fh' to get MJ plan and '-o -fh -fm' to test NL plan.
>
> Vadim
>
Ciao
Das Boersenspielteam.
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